This invention relates to a method of securing a tubular element of any desired cross-section into an aperture in a support and has particular but not exclusive application to the securing together of tubes and tube plates in the formation of heat exchangers. The invention also embraces apparatus for performing the aforesaid method.
Conventional methods of securing together tubes and tube plates employ techniques such as fusion welding, brazing or soldering, or various mechanical processes such as roller expansion, drifting with the aid of an oversize tool to expand the tube, or rivetting. Although some of these methods are widely used in industry and are thought to be generally satisfactory, they can give rise to such problems as lack of the necessary high joint integrity, residual corrosive products of the joining process which have to be removed, and excessive space requirements.
An object of the invention is to provide a method of and apparatus for securing a tubular element into an aperture in a support in which the aforesaid problems are alleviated or avoided.
According to the invention, a method of securing a tubular element into an aperture in a support, comprises the steps of inserting the tubular element into said support aperture, bringing an ultrasonic vibratory tool, of maximum transverse dimension slightly greater than the internal maximum transverse dimension of the bore of the element, into axial alignment with the bore, and, with the element axially supported, applying axial force to the tool whilst vibrating it ultrasonically so as to move it into the bore and expand the element outwardly against the wall of said aperture.
In a particularly effective form of the method, a counterbore is formed in the end portion of the support aperture facing the tool and the element is expanded into the counterbore.
From another aspect of the invention, apparatus for carrying out the aforesaid method comprises means for rigidly holding a tube support in a desired position, means for supporting a tubular element with an end portion thereof within an aperture of the tube support, a tool of maximum external dimension of the element, means for vibrating the tool ultrasonically, means for applying a force to the tool in a direction longitudinally of the element, and abutment means for engagement by the element to provide a reaction to said force during application of the tool to the element to expand the latter.